Home Forums Help/Technical Questions big muff american reissue very low output

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  • #81440
    khandley
    Member

    i’ve been wrestling with my big muff for a while to bring it back to life

    i’ve seen a lot of posts of things like this or similar but they seem to get abandoned

    when the pedal is off, it bypasses perfectly but when engaged the volume pot has to be up all the way to hear something.

    you can hardly call it output.

    i’ve replaced the vol pot and checked all wiring and everything seems fine

    don’t really have any money to get it fixed at the guitar shop

    any diy help would be appreciated

    #114581
    The EH Man
    Moderator

    Have you tried audio tracing?

    #115287
    Frobro808
    Member

    Hey guys im new here and this is my first post! Im sorry to have zombied this thread…
    I have the same problem and bynthe time I have enough signal, the noise and the actual effect are the same level. And what exactly is audio tracing.

    #116578
    derekb
    Member

    actually having the same issue on a spare big muff pi I have lying around, has anyone ever figured out the likely culprit for this? effects appear to work but unless you crank volume to max on the pedal, you cant even hear anything, and even then what you can hear is muffled by pedal hum. Any solutions?

    #116584
    scottv
    Member

    It could be a number of issues, an audio trace is I believe like an “audio probe” there is a step by step guide on DIY stompboxes dot com on how to do this, basically its using a cable with a signal source plugged into it on one end (something that gives a constant sound, plucking a guitar is too cumbersome, so maybe a portable cd player or ipod) and capacitor on one lead of the opposite end and the other lead grounded. use the open lead of the capacitor as “the probe” contacting various places on the circuit board, not randomly as you should “trace” through the circuit from start to end, the output of the circuit is plugged into an amp to listen for the input signal, what this will find is if there is:

    bad solder point or trace on the circuit bad

    or

    bad component (capacitor, transistor, diode… resistors are tougher to destroy but…)

    #116585
    The EH Man
    Moderator

    Check at the center lug of the Volume control. If it’s loud there it’s probably a footswitch issue.
    Check the center pin of each transistor for signal. If it’s there then it’s got through the previous stage OK.

    #116590
    derekb
    Member
    Quote:
    It could be a number of issues, an audio trace is I believe like an “audio probe” there is a step by step guide on DIY stompboxes dot com on how to do this, basically its using a cable with a signal source plugged into it on one end (something that gives a constant sound, plucking a guitar is too cumbersome, so maybe a portable cd player or ipod) and capacitor on one lead of the opposite end and the other lead grounded. use the open lead of the capacitor as “the probe” contacting various places on the circuit board, not randomly as you should “trace” through the circuit from start to end, the output of the circuit is plugged into an amp to listen for the input signal, what this will find is if there is:

    bad solder point or trace on the circuit bad

    or

    bad component (capacitor, transistor, diode… resistors are tougher to destroy but…)

    sounds interesting, any chance you ahve a link to the guide?

    #116595
    scottv
    Member

    http://www.diystompboxes.com/wiki/index.php?title=Debugging

    2nd section from the top is on using an audio probe.

    #116596
    derekb
    Member

    thanks for the link

    On some additional fiddling I found what seems to be the problem, the tone knob is cutting out completely once turned past 12 o clock.

    On further inspection, it seems the Tone knob cuts out the output unless I pull the knob physically upwards away from the unit. Should I just replace the potentiometer?

    #116600
    scottv
    Member

    it might be the pot, i would use a multimeter on it and check the resistance at various points in its rotation. that may give you a clue if its bad.

    #116601
    derekb
    Member
    Quote:
    it might be the pot, i would use a multimeter on it and check the resistance at various points in its rotation. that may give you a clue if its bad.

    it certainly seems to just be the pot, once the knob is lifted about a millimeter out of the socket it rests in it clicks back in, and theres no physical movement on any other component since its secured in place. will replace and see what happens

    #116757
    warthog
    Member

    This is exactly what is happening with my muff and the tone knob! any updates on your fix?????

    a

    #116758
    derekb
    Member
    Quote:
    This is exactly what is happening with my muff and the tone knob! any updates on your fix?????

    a

    actually yes, the pot would lose contact if not holding the knob slightly vertically up, so as a ghetto solution I inserted a small rubber o-ring into the gap created when pulling the pot stem. This keeps the knob held up and in contact, it adds some resistance to turning, but hey, it works!

    #116759
    warthog
    Member
    Quote:
    Quote:
    This is exactly what is happening with my muff and the tone knob! any updates on your fix?????

    a

    actually yes, the pot would lose contact if not holding the knob slightly vertically up, so as a ghetto solution I inserted a small rubber o-ring into the gap created when pulling the pot stem. This keeps the knob held up and in contact, it adds some resistance to turning, but hey, it works!

    THanks! I’ll give it a try.

    A

    #116760
    The EH Man
    Moderator

    I have seen this on some other EH pedals but not on Big Muffs. What you can do is open the pot up and bend the wiper contacts out a bit then reassemble the pot.

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